Mai, who has a perfect stepbrother, has dreamed of marrying him since she was little, reasoning, "We're not blood relatives, so I'm definitely going to marry my brother!" However, she then remembers that her stepbrother is a character from a death game manga, who will host a death game involving his classmates one year later, and in the process, kill Mai, his sister. Remembering her stepbrother's line from the manga, "Everything is going as expected, and it's boring," Mai begins to plan various pranks for him every day. However, as days pass, her stepbrother starts exhibiting increasingly deranged tendencies...

This is a re-publication of "I Reincarnated as the Sister of the Mastermind Murderer Who Leads All Classmates in a Death Game Manga to Their Deaths and Failed" (originally 2018~) and a revised edition of "I Reincarnated as the Sister of the Mastermind Murderer in a Death Game Manga and Failed [Complete]" (originally 2019~).

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